In the end, it wasn't the attorney general's federal lawsuit, the Vermont Legislature, the Public Service Board or any of those pesky enviros nitpicking about underground tritium leaks and collapsed cooling towers that shut down Vermont Yankee.

It was the invisible hand of the marketplace.

On Tuesday, New Orleans-based Entergy Corporation announced plans to close the Vermont Yankee Nuclear Power Station in Vernon by the end of 2014. Praising Vermont Yankee's talented, committed and dedicated workforce, Entergy chairman and CEO Leo Denault called it "an agonizing decision and an extremely tough call for us."

Denault touched on some of the economic forces that compelled Entergy's decision, including a "transformational shift" in the natural gas market that has driven down electricity-generation costs, high maintainence costs on the 41-year-old trouble-prone plant and "wholesale market design flaws" that have kept energy prices "artificially low" throughout New England.

So what happens next? Presumably, the plant spends the next decade or more decommissioning the plant and cleaning up the radiation. According to Entergy's press release, the Vermont Yankee decommissioning trust has a balance of $582 million, in excess of the Nuclear Regulatory Commission's minimum financial assurance of $566 million for terminating the plant's license.

Gundersen, who provided expert testimony recommending the closure of five of the six nuclear plants nationwide that were eventually deep-sixed this year, says he was right that Vermont Yankee was neither economically viable nor safe enough to remain open for another 20 years, as Entergy argued when its operating license was extended last year.

"Vernon has lived in fantasyland since 2012," Gundersen says. "If they believed that they had a 20-year relationship with Vermont Yankee, they may have thought it was a 20-year marriage, but Vermont Yankee thought it was 20 years of one-night stands. There was never any commitment on [Entergy's] part to see this thing through."

Vermont Yankee won't be gone in the morning. According to Gundersen — and he has a solid track record predicting VY outcomes — there's not enough money in the decommissioning fund to begin work right away. He suspects that if the plant is mothballed for another 10 years, enough money should accumulate in the fund to begin the decade-long process of dismantling the facility. He thinks the entire process can be finished within 20 years.

What happens until then? Once Vermont Yankee "pulls the plug," Gundersen explains, they'll have to drain all the radioactive fluids and get the nuclear fuel out of the reactor, which will then be stored for five years. After that, the fuel can be put into dry-cask storage and the reactor license officially terminated. But for five years, Vermont Yankee will need to keep its maintenance people, engineers, security and other staff onsite to ensure the plant's safety. Yankee currently employs 630.

"So, there will be people employed there for five years doing what they've done all along," Gundersen says.

Once all the radioactive material is out of the plant, Entergy will have to get rid of the hot "carcass." How long that empty shell sits there, Gundersen says, will depend upon how much money is in the decommissioning fund. Gundersen believes the cleanup will cost $250 million more than what's in there now.

"Let's hope the stock market doesn't collapse again," he suggests.

Based on Gundersen's experience decommissioning of other nukes around the country, he recommends that Vermont regulators remain diligent watching for underground leaks of radioactive material, including cesium, cobalt and strontium which are "incredibly difficult to detect from above."

Such a leak at Connecticut Yankee, he notes, raised the cleanup costs by about $1 billion.